Help with 2.5 NAD Fuel System (Picture or Schematic) - Defender Source
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  #1  
Old February 15th, 2016, 03:35 AM
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Help with 2.5 NAD Fuel System (Picture or Schematic)

I've dropped-in a 2.5 NAD and I'm trying to put it together. Can someone take a picture of the fuel filter housing and all the connections (to include fuel feed, fuel return and connections to injector pump) on their 2.5 NAD, or does someone have a schematic?

A different, but related problem I am having right now is that my new diesel pump fittings and the old diesel line fittings coming from the fuel filter housing are different sizes. I may have to take the fitting off my old pump too make it work, or buy new fuel lines. It's odd, the threads for the fittings coming out of the filter housing are the appropriate size for the diesel pump, but the fitting on the other half of the line are larger and will not fit. Ugh...

Thanks
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  #2  
Old February 15th, 2016, 08:33 AM
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Robert Davis
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Ed:
The original fuel flow for the 2.5 N/A is not optimal as it redirects the spill over and the return line from the IP back to the fuel filter via the plastic line with 1/2 X 20 UNF fittings.
This routes trapped air back into the filter where it recirculates making bleeding the system much more difficult than it needs to be.
All the new Bosch spin-on filters including the TDI spin-on filters have 14mm X 1.5.

The optimal routing for a self bleeding fuel system is:
Tank -> Sedimenter -> 12V fuel pump -> lift pump -> filter -> IP -> return line from IP joins with Injector spill over -> straight back to the tank.
Assuming you have barbed fittings, you can run new rubber fuel line and use hose clamps on the metal barb fittings.
The plastic line should easily come off the original metal fittings with a wire brush wheel.
We have a drawer full of fittings if you need any, but they should be plentiful in Germany.
I am no fan or the original plastic lines that over time split and leak or develop leaks when kinked.
Have fixed many vehicles with bad plastic line and as such never use it.
Some owners cut the plastic line and insert into rubber fuel line and then clamp the union.
Bad idea as the plastic line will collapse inside the rubber hose and stop or severely restrict flow.

Hope this helps
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  #3  
Old February 15th, 2016, 02:07 PM
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Quote:
Originally Posted by rdavisinva View Post
Ed:
The original fuel flow for the 2.5 N/A is not optimal as it redirects the spill over and the return line from the IP back to the fuel filter via the plastic line with 1/2 X 20 UNF fittings.
This routes trapped air back into the filter where it recirculates making bleeding the system much more difficult than it needs to be.
All the new Bosch spin-on filters including the TDI spin-on filters have 14mm X 1.5.

The optimal routing for a self bleeding fuel system is:
Tank -> Sedimenter -> 12V fuel pump -> lift pump -> filter -> IP -> return line from IP joins with Injector spill over -> straight back to the tank.
Assuming you have barbed fittings, you can run new rubber fuel line and use hose clamps on the metal barb fittings.
The plastic line should easily come off the original metal fittings with a wire brush wheel.
We have a drawer full of fittings if you need any, but they should be plentiful in Germany.
I am no fan or the original plastic lines that over time split and leak or develop leaks when kinked.
Have fixed many vehicles with bad plastic line and as such never use it.
Some owners cut the plastic line and insert into rubber fuel line and then clamp the union.
Bad idea as the plastic line will collapse inside the rubber hose and stop or severely restrict flow.

Hope this helps
Okay, this is great news! So, I just removed a 300 TDI with a spin-on filter that had only an input and an output connection, vice the octopus looking thing that I installed as part of the old 2.5 NAD. I am assuming I should just keep that and re-use all the lines instead of struggling with the old filter system. Guess I need to go look at the 300 TDI and pull the requisite pieces and parts. Will probably solve my IP and fuel line fitment issue too.

Now for the stupid questions:
1. Are the sedimenter and 12V fuel pump stock? I have not run into them yet, but haven't been looking for them.
2. How does, "return line from IP joins with Injector spill over" work? A barbed "Y" connection?
3. Will the setup be similar to the old 300 TDI setup? That would certainly be serendipitous.
4. Do you have a schematic of what you are explaining above? First I've ever messed with a fuel system.

Thanks again for your help. Super news, as I just had to buy a 38 Euro banjo fitting and line that doesn't even fit...ugh.
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  #4  
Old February 15th, 2016, 02:25 PM
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You asked:
Now for the stupid questions:
~No question is stupid~

1. Are the sedimenter and 12V fuel pump stock? I have not run into them yet, but haven't been looking for them.
~The TDI vehicles and most British Diesel powered vehicles sport the sedimenter. The 12V diesel fuel pump is an add on that works great and renders a self bleeding fuel system.~

2. How does, "return line from IP joins with Injector spill over" work? A barbed "Y" connection?
~Via a T or Y joining the 8mm return to the 3mm injector spill over line~

3. Will the setup be similar to the old 300 TDI setup? That would certainly be serendipitous.
~similar, but not identical, but you can use the TDI spin-on fuel filter~

4. Do you have a schematic of what you are explaining above? First I've ever messed with a fuel system.
~I do not, but it is so straight forward simple, do not think one will help as each device is in out or both in and out.~

Thanks again for your help. Super news, as I just had to buy a 38 Euro banjo fitting and line that doesn't even fit...ugh.
~Good Luck~
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RDavisinVA

Uncle "Richard" Douglas has a Land Rover with big wheels that never gets stuck... until he breaks something so it won't go. Uncle Douglas always breaks something. - Anna Crowther at the Conclave 2012 (AKA Carburetor Neck)

"What's with this death wobble, Uncle Douglas, I can't keep it in 1 lane?"
UD: "Just Power through it man!"
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Old February 21st, 2016, 01:42 PM
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Okay, got everything except the injector return line hooked-up. That's temporarily feeding into a clear jar until I can find a barbed T or Y.

Unfortunately, I have a problem. No fuel is coming-out of the bleed screws in the new injector pump. While assembling the system, I had fuel from the lift pump (pumping manually) going into the filter and coming out the line going into the injection pump; however, nothing appears to be going into the injector pump and up into the injectors.

I could only find a schematic of the 300 TDI setup. The only thing I can think of is I may have the feed line going into the wrong connection on the injection pump. It's going into the rear of the pump, closest to the lines going into the injectors. Is this right? I didn't have time today to switch the lines, but I strongly suspect this may be the problem.

In additionn, I'm only getting 9 volts into the injector pump solenoid while cranking. Is this voltage drop normal? Will the pump still work with 9 volts instead of 12?

Thanks
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Old February 22nd, 2016, 07:21 AM
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Okay, I put 12 volts to the solenoid and it clicked (good solenoid). I then put a jumper wire on it btwn the positive terminal on battery and the terminal on solenoid. After cranking a few seconds, I get fuel to the injectors (cracked the lines a tad to bleed while cranking).

So, it appears the fuel lines are set-up correctly and fuel is now getting to the injectors, but I'm not getting 12 volts to the solenoid. When should I see the 12 volts to the solenoid -- position I (accessories), II (glow plugs and run), or III (start)? I'm assuming position II, but I may have the positions all dorked in the last sentence;-)
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Old February 22nd, 2016, 08:22 AM
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You'll need a relay.
Use the 9V to trip the relay contacts and the 12V brown to the fuel solenoid.
Relay 86 - your current 9V wire
85 ground(-)
30 (+) 12V Brown
87 (+) 12V to your fuel solenoid
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RDavisinVA

Uncle "Richard" Douglas has a Land Rover with big wheels that never gets stuck... until he breaks something so it won't go. Uncle Douglas always breaks something. - Anna Crowther at the Conclave 2012 (AKA Carburetor Neck)

"What's with this death wobble, Uncle Douglas, I can't keep it in 1 lane?"
UD: "Just Power through it man!"
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Old February 26th, 2016, 11:41 AM
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Quote:
Originally Posted by rdavisinva View Post
You'll need a relay.
Use the 9V to trip the relay contacts and the 12V brown to the fuel solenoid.
Relay 86 - your current 9V wire
85 ground(-)
30 (+) 12V Brown
87 (+) 12V to your fuel solenoid
Thanks. I don't see a relay in the schematic I have. Of course, the schematic is in the back of the Haynes manual, so the source is suspect.

From what I can tell, the fuel cut-off solenoid is fed by a 12V line straight from the ignitiion switch. I haven't had any time to check my switch, but something tells me that either the wire came off, or I have a short. Will be looking at it next weekend.
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Old March 5th, 2016, 10:18 AM
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I have fixed the solenoid. I've been cranking and bleeding the fuel filter assembly, but the engine is not catching. I'm still not seeing fuel from the bleeder valve on my DIP - bone dry. I've cracked the injector lines and there is fuel present, but it's not coming out as I expected -- it surges while cranking as expected, but just dribbles out. What Bar or PSI should I expect? Thought it would be pretty high -- much higher than what I am seeing.

The engine is cranking over pretty slow too, so that may be why I'm not getting a whole lot of pressure in the lines?

Thanks
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